[BUG] git push writes to stderr instead of stdout on success

`git push` writes to stderr instead of stdout

Steps to reproduce:

  mkdir foo
  cd foo
  git init
  echo foo > fo
  git add -A
  git commit -am "foo"
  git push . HEAD:refs/heads/newbranch 2>out

Expected: `out` file is empty

Actual: `out` file contents:

To .
 * [new branch]      HEAD -> newbranch